Can you explain why the transaction date is considered the completion date, so I can remember it clearly?

The reason the HDB resale transaction date shown in records is the completion date—and not the application date—is because the completion date is the legal point at which ownership transfers from seller to buyer, keys are handed over, and the new owner can officially move in. This date marks when all payments are settled, documents are signed, and the transaction is finalized according to HDB regulations. It serves as the most definitive reference for when the property actually changes hands and is recognized as the official historical sale record for that flat.